Power output regulation of internal combustion engines is necessary. This is typically accomplished by using a throttle valve to restrict the amount of air admitted to the engine when less than full power output is required. In addition, turbochargers and superchargers are used to increase engine air charge well above that inducted with normal atmospheric pressure and wide open throttle.
At throttle valve positions less than wide open, increasingly significant air flow work must be done by the engine itself in order to induct less and less air. This is because the typical engine inducts a fixed volume of air per revolution and thus can only induct a lower weight of air by drawing from a source that has been reduced in pressure by some means. This flow work can be understood by realizing that whenever the engine is drawing upon a low pressure source of air, it must still exhaust to atmospheric pressure. The net flow work required is thus equal to this net pressure differential times the engine intake displacement.
Screw type machines are currently in use for the supercharging of internal combustion engines. However, they function only in the compression mode and do not, by themselves, serve to control the air flow to the engine. Other control means such as throttle valves and bypass valves are used for the airflow control to the engine. These current superchargers have no need for a unique rotor profile such as is described in the already mentioned copending application.
The concept of screw type machines alternately working as a compressor or an expander already exists in the prior art. Such a device is conceptually shown in U.S. Pat. No. 4,220,197 of which the current applicant is a patentee. However, that screw device in the form of a helical screw rotary compressor/expander was conceived to act as an air conditioning compressor whenever that function was required in its vehicular application. When air conditioning was not required, the device would then act to recover energy from refrigerant which was first vaporized at high pressure by heat exchange with the vehicle exhaust gas. Two slide valves are incorporated in the compressor/expander for control purposes. High pressure refrigerant is admitted to the device when expansion (for energy recovery) is taking place and low pressure refrigerant is admitted when compression (for air conditioning) is taking place. This particular device was never reduced to practice, yet stands as prior art to the instant invention.
After study, it became apparent to the present inventor that the throttle valve in an automotive engine causes a significant waste of developed power whenever the engine is operating at reduced power outputs for a given speed. This loss comes about because the engine is caused to intake under a vacuum condition yet must finally exhaust to atmospheric pressure.
It is a primary object of the present invention to provide an internal combustion engine system which allows the necessary variation in automotive engine power output for a given speed but which also works to eliminate the engine intake throttle loss.
It is a further object of the present invention to provide an internal combustion engine system utilizing a positive displacement compressor/expander feeding combustion air to the engine intake manifold in which the compressor/expander functions preferably for supercharging the air, in which complete engine air flow control is accomplished with a single valve eliminating the conventional engine throttle valve resulting in immediate throttle response at slow engine speed with increased supercharger compression efficiency and with increased vehicle mileage by utilizing energy recovery during engine intake manifold vacuum conditions.